Physiology Midterm- Sensory Physiology Flashcards
Sensitivity
Ability to localize where stimulus is without looking at it
Transducer
Something that converts one form of energy to another
Ie. retina converts light energy to electrical
What happens if a sensory neuron does not spike?
No sensation
Peripheral receptive field
Specific region of skin which a receptor monitors
-Usually applies to touch receptors
Body parts with peripheral receptive fields smallest in area
Fingertips and lips
Where are larger Peripheral receptive fields found?
In areas requiring less need for sensitivity, ie. on your back
Where is greatest overlap of peripheral receptive fields?
Areas that require greater sensitivity
Fingertips and lips
More overlap of peripheral receptive fields= (more/less) sensitivity
More
Specific energy
Type of energy that the receptor is most sensitive to
How is the stimulation of light receptors always perceived by the brain as?
Light
Can other types of energy stimulate a different energy receptor?
Yes
Ie. you can rub your eye(mechanical stimulus) and stimulate the light receptors and perceive light
Two point discrimination
Stimulating 2 points on the body to determine the minimum distance apart that the person can tell that there are two stimuli occurring
Hyperesthesia
Patient does not have adaptation with sensory stimuli
Receptor adaptation
How fast the fiber will accommodate to stimuli
What kind of receptors are the fastest adapting receptors?
Touch receptors on skin and hair receptors
Slowest adapting receptors
Pressure receptors in carotid artery
Labeled lines
Refers to how the receptors are attached to CNS, which tells the brain how to locate where stimulus is coming from
Phantom limb
Feeling a sensation in a limb that has been removed and is no longer there
What causes phantom limb pain?
Nerve trunks that are still present in the stump that correlate to the part of the limb that has been removed can still be stimulated, causing the brain to perceive a stimulus in the nonexistent limb
Generator potential
Depolarization of nerve ending
What does a generator potential do?
Will cause membrane potential to move toward 0
Basic properties of generator potentials
- They are depolarizations
- The greater the stimulus, the larger the generator potential
- Travel by electrotonic conduction
- They can sum
Trigger zone
Region on membrane near the specialized sensory ending where the spike is initiated if threshold is surpassed
Voltage clamping
Process by which the general potential remains as long as the stimulus is in contact with the sensory ending
What is the generator potential magnitude determined by?
Stimulus intensity (higher stimulus intensity=higher GP)
Rhythmic discharge
Several spikes in sequence
What causes rhythmic discharge?
As repolarization proceeds to the level of membrane charge the cell is clamped at, you will get another spike
What causes faster repetitive rates of spikes?
Larger generator potential
Frequency coding
Brain can estimate the intensity of the stimulus you experience by the frequency of firing of the sensory nerve
What is the rate of discharge measured in
Spikes/sec
Relationship between intensity of the stimulus and how the brain perceives it
^stimulus intensity, ^generator potential
^generator potential, ^rate of discharge
^rate of spikes, brain perceives as ^intense stimulus
How does the CNS know exactly where a stimulus is occurring and how intense it is?
Property of frequency coding combined with the property of labeled lines
Classes of receptors
Mechanoreceptors
Thermoreceptors
Chemoreceptors
Nociceptors
Pain sensation theories
Specificity theory
Pattern theory
Specificity theory
Receptor specific for pain sense
- problem: does not explain what sort of specific energy pain is
- true because nociceptors respond to prostaglandins and kinins that are produced as a result of inflammation due to damaged tissue
Pattern theory
Brain sensed pain by the pattern of spike discharge of receptors of various specific energies
-true because if a rate of firing passes a certain threshold it is perceived as pain (Any type of receptor)
Gate control of pain
Non-nociceptive sensory fibers branch as they enter the spinal cord and provide IPSP input to pain pathways.
Pain, touch, and temperature information are all carried by the same tract and are in close proximity, allowing the interneurons to attach in this manner
Gate control of pain provides evidence for what therapeutic modalities?
TENS (transcutaneous electroneural stimulation) Acupuncture Massage Heat Cold
Referred pain
Sensation of pain in a structure that is not injured. The pain comes from a different structure that is injured
Why does referred pain happen?
During fetal development, structures shared the developing ectoderm that later became neural tissue. As development proceeds , the structures separate but still share the same neuronal pool in the spinal cord.
Redicular pain
Pain resulting from nerve irritation
Example of referred pain
Patients with supraspinatus tendinitis typically also end up with pain in the C5 dermatome
Example of redicular pain
Pain down the leg due to bulging disk pressing on nerve trunk
